This application presents plans for a broad approach to the problems of cancer biology featuring the study of cells infected and transformed by RNA and DNA tumor viruses. Plans in five areas are described. I. Growth regulation in virus infected cells; II. Viral and cell membranes; III. Biology of RNA tumor viruses; IV. Genetic expression in mammalian cells: normal and DNA tumor virus infected; V. Control of gene function at the level of transcription, mRNA processing and translation.